<h3>Tree3</h3>
<!-- 
    nzDraggable	设置节点可拖拽
    nzBlockNode 是否节点占据一行  没看懂是啥意思
    nzOnDrop    drop 触发时调用
 -->
<nz-tree [nzData]="nodes" nzDraggable nzBlockNode (nzOnDrop)="nzEvent($event)"> </nz-tree>
